1. Field of the Invention
The present invention relates to a transmitting/receiving antenna for transmitting an electric power and transmit data to a radio communication medium such as an IC tag attached to a goods, a book, etc., a non-contact IC card used for personal authentication, or the like and receiving receive data from the radio communication medium, and a transmitting/receiving device using this transmitting/receiving antenna.
2. Description of the Related Art
Commonly, the system that is called the “non-contact IC card system” utilizes a frequency band of 13.56 MHz, for example. Such system is proceeding toward practical use in physical distribution systems, traffic system, commodity control system, book management system, personal authentication system, and others.
Concretely, the electric power and the transmit data are supplied to the radio communication medium such as the IC tag attached to the goods, the book, etc., the non-contact IC card used for the personal authentication, or the like from the transmitting/receiving antenna of the transmitting/receiving device.
Also, the receive data transmitted from the radio communication medium is received via the transmitting/receiving antenna, and is processed by the transmitting/receiving device.
Also, the utilization of the radio communication medium is proceeding recently in the fields of security system, electronic money, personal authentication, and the like. Such a demand is escalating that one transmitting/receiving device should be enabled to cope with the circumstances where plural types of communication systems whose communication method is different respectively are mixedly utilized.
Therefore, in order to fulfill such demand, i.e., in order to enable one transmitting/receiving device to cope with the circumstances where plural types of communication systems whose communication method is different respectively are mixedly utilized, such a proposal has been made that a wider frequency band of the frequency characteristic should be implemented by switching sequentially a plurality of resistors (resistance values) that are interposed into a transmitting/receiving channel of the transmitting/receiving antenna (see Patent Literature 1, for example).
Patent Literature 1: JP-A-2007-199871
As described above, in the technology disclosed in Patent Literature 1, a plurality of resistors (resistance values) connected to the transmitting/receiving antenna are switched sequentially to realize a wider frequency band of the frequency characteristic. In this case, as the result that the resistors are always interposed in the transmitting/receiving channel of the transmitting/receiving antenna, such a problem arises that a loss caused due to the resistors causes an increase in the power consumption.